1. Field of the Invention
The present invention relates to novel phosphors and light-emitting devices using the same and, more particularly, to novel phosphors capable of being excited by blue light or UV light and light-emitting devices using the same.
2. Description of Related Art
Phosphors have been applied in lighting devices and display devices for a half century. Taking the most widely used fluorescent lamps for example, phosphors applied therein can be excited by mercury radiation as excitation light and then emit visible light. The light color emitted from a fluorescent lamp can be modified by mixing various phosphors and wide range of color temperature and color rendering characteristics for light output can be achieved, resulting in its wide application. However, most of commonly used three-basal-color phosphors have disadvantages of high cost due to that these phosphors often use limited reserves of rare elements (such as Eu, Ce, Tb etc.) as raw materials.
Recently, white light-emitting diodes (W-LEDs) also have been actively developed due to their high luminescence efficiency, low power consumption, long lifetime and environment friendly features in comparison with traditional lighting devices and thus are considered most potential to replace fluorescent lamps. For white light-emitting diodes, the methods of making white light include: as a first type, mixing light from red, green and blue LED chips in a white light-emitting module; as a second type, mixing light from a blue LED chip and yellow YAG phosphors that can be excited by the blue LED chip; and as a third type, mixing light from red, green and blue phosphors that are mixed with an optically transparent resin and can be excited by an UV LED.
Most of commercially available white LEDs apply the above-mentioned second method to emit white light. However, the second technology was claimed for a patent by Nichia. Accordingly, it is necessary to develop novel materials to overcome patent barrier.